Normal Saline Solution (NSS) is commonly used in various laboratory procedures like in the preparation of Red cells Suspension for the crossmatch, for preparing dilutions of Reagents, for stool examinations, to make the dilutions in serological tests, diagnostic tests etc.
There are commercially prepared Normal saline solution available in the market but it can easily be prepared manually in the laboratory whenever required. The normal saline solution is simply the 0.85% Sodium chloride (NaCl) solution which can be prepared in the laboratory by dissolving the calculated amount of Sodium chloride crystals in the required quantity of Distilled water.
The Normal saline solution is prepared as follows……
CALCULATION FOR NORMAL SALINE SOLUTION…..
⇒ A normal saline solution is the 0.85% sodium chloride solution.
⇒ That means 0.85 gm of sodium chloride in 100 ml distilled water.
⇒ For preparing 1 L normal saline solution we require,
W1 / V1 = W2 / V2
W1 = Required quantity of sodium chloride for 100 ml NS = 0.85 gm
V1 = Required volume for 0.85 gm sodium chloride to make NS = 100 ml
W2 = Required Quantity of Sodium chloride to make the desired quantity of Normal Saline solution
V2 = 1000 ml (or desired quantity of Normal saline to be prepared)
0.85 gm / 100 ml = W2 gm / 1000 ml
0.85 gm × 1000 ml = W2 × 100 ml
W2 = 0.85 × 1000 ml / 100 ml
W2 = 8.5 gm
Thus, to prepare 1000 ml of Normal saline solution 8.5 gm sodium chloride crystals should be dissolved in 1000 ml of distilled water.
- Weighing scale
- Volumetric flask/beaker
- Distilled water
- Sodium chloride (NaCl)
PROCEDURE FOR NORMAL SALINE SOLUTION…..
⇒ Weigh 8.5 gm of Sodium chloride (NaCl) with the help of weighing scale.
⇒ Now take 500 ml of distilled water in the volumetric flask or in a Beaker and to this add 8.5 gm NaCl.
⇒ Swirl the flask gently to mix the contents or stir in case you are making the solution in a beaker with the help of stirrer.
⇒ When NaCl dissolves completely then add distilled water and make the final volume 1 liter.
⇒ Insert an air-tight stopper into the mouth of the volumetric flask and shake it gently to make the solution homogeneous or if you are using a beaker stir the solution well using a stirrer.
⇒ Now Autoclave the prepared normal saline solution at 121 °C, 15 psi pressure for 15 minutes. This will sterilize the solution and made it the Laboratory grade Normal saline solution which can be used in pathological as well as microbiological analysis.
⇒ If you have prepared the Normal saline in a beaker transfer it to the volumetric flask or Erlenmeyer flask and autoclave it at 121 °C, 15 psi pressure for 15 minutes.
In this way the Laboratory grade Normal saline solution is prepared in the laboratories.